Method of hardening gelatin by reacting with conjugated heterocyclic compounds containing halogen atoms and water-solubilizing acid groups



United States Patent M 3 288 775 METHOD OF HARDENING GELATIN BY REACT-ING WITH CONJUGATED HETEROCYCLIC COM- POUNDS CONTAJNING HALOGEN ATOMSAND WATER-SOLUBILIZING ACID GROUPS Walter Anderau, Aesch, Basel-Land,and Alfred Oetiker,

Basel, Switzerland, assignors to Ciba Limited, Basel,

Switzerland, a Swiss company No Drawing. Filed Apr. 2, 1962, Ser. No.184,581

6 Claims. (Cl. 260-117) In the manufacture of photographic layersgelatin is preferably used as the hydrophilic colloid which containssilver halides and, if desired, color couplers or dyestuffs, the gelatinbeing cast on to a suitable support, for example, a film, paper or glassplate. After being dried and exposed, these layers are introduced intonumerous treatment baths, such as developing baths, fixing baths and, ifnecessary, image reversal baths or color bleaching baths. During thesetreatments the gelatin layers swell considerably, and gelatin may bepartially dissolved away or even completely washed off.

In order to make the gelatin layers more resistant to the attack of thetreatment baths they are hardened, that is to say, their swellingcapacity in water and in the baths is decreased and the melting point ofthe aqueous layers is raised from the original 28 to 30 C. up to 60 to95 C., or even so high that the gelatin can withstand treatment at theboiling temperature of an aqueous bath.

The conventional hardening agents include aldehydes, preferablyformaldehyde, and chromium salts and alums. In the form of diluteaqueous solutions these hardening agents may either be added to thefinished emulsion prior to casting or'used as an initial treatment bathor as an intermediate bath during the processing treatment.

The use of the conventional hardening agents has certain disadvantages.The action of the chromium salts is often very dependent on the pH-valueof the cast mixtures. Alums have the same disadvantage in processingbaths. When known hardening agents are added to the finished emulsionsprior to casting, a viscosity variation dependent on time often occurs,so that the viscosity increases slowly during the casting operation andthus causes variation in the thickness of the layer. The aldehydes canalso lead to fogging, especially in the case of highly sensitized silverhalide layers. Color fog can also be caused by the hardening agent.

There is therefore a need for hardening agents that can be added tofinished emulsion prior to casting without causing a change in viscosityduring the casting operation, and which, Within a short time aftermanufacture of the material, for example, 1 or 2 days or, if necessary,after 15 to 40 days, give a degree of hardness that permits the materialto be used and tested in the normal manner and do not cause the layersto become horny during long periods of storage. Furthermore, suchhardening agents should not cause fogging, and should exhibit a neutralbehaviour towards color couplers and any other additions.

The present invention is based on the observation that gelatin can behardened in an advantageous manner by reacting it with a colorlesscompound which contains at least one acid group imparting solubility inwater, at least one heterocyclic six-membered ring consisting of 3 to 4carbon atoms and 3 to 2 nitrogen atoms, and at least one halogen atombound to a carbon atom of the six-membered ring.

By reaction is meant a chemical reaction between the gelatin and thehalogenated six-membered ring, for example, a halogen-triazine ring, toform a homopolar bond.

The compounds to be reacted with the gelatin must contain at least oneacid group imparting solubility in water, for example, a carboxylic acidor l-lO S-group, which may be present as a sulfonic acid group (bound to3,288,775 Patented Nov. 29, 1966 Halogen-C 0 -Halogen C C R 'I IH .Eialogen Halogen N C R NHG C-Halogen Halogen Halogen K Halogen-OC-Halogen HiLR.

( Halogen N O R1-NH- 0 CH Halogen Halogen N' C Halogen-0 CH alert,

( Halogen Halogen-C OH (I) O NHR 1 Halogen Halogen0 C==SO NH-R\ N: C H

in which R represents an organic radical containing at least one acidgroup imparting solubility in water, and also compounds of the generalformulae in which R represents an organic radical containing at leastone acid group imparting solubility in water, and R represents a halogenatom or an organic radical containing at least one acid group impartingsolubility in water, a hydrocarbon radical or a substituent bound to thetriazine ring through an oxygen, sulfur or nitrogen atom.

At least one of the radicals R and R is advantageously composed of anoxygen or nitrogen atom bound to the 1:3 z5-triazine ring, a hydrocarbonradical, advantageously an aliphatic hydrocarbon radical, or a radicalof the benzene or naphthalene series, and at least one carboxylic acid,sulfonic acid or sulfato group. Both radicals may have this constitutionand they may be identical or difierent from each other,

Alternatively, only one of the radicals R and R may have the aforesaidconstitution and the other may be a halogen atom or a hydroxyl ormethoxy group, or a phenoxy or amino group which may be substituted. Ex-

amples of such radicals are:

CH; CH; C2115 -06, N/ N -N/ \H oH, onn CHrCHz-OH CHa-CHz-OH CHr-OHzOH -N-N -N \H CHrCHr-OH oH,

The compounds may also contain two lz3z5-triazine rings linked togetherby a bridge, for example the divalent radical of a diamine, such as1:4-diamino-benzene or an alkylene diamine.

The following are examples of radicals R and R which contain an acidgroup imparting solubility in water:

-Nnorr2 ooon SOa CODE

SOBH SO H SOQH

Thus, for example, the following halogen compounds may be reacted withgelatin:

b SO H C-HN-CHa-CO OH SOJH X=H, SRQH or OOOH N=N I SO H I Theheterocyclic compounds used in the method of the invention, especiallythe halogen-1:3z5-triazines, can be made by methods in themselves known.For example, an amino-benzene sulfonic acid may be condensed in a weaklyacid medium With freshly precipitated cyanuric chloride. In order toexchange a second halogen atom for the radical of an amine or of anamino-sulfonic acid, the primary condensation product so obtained may bereacted at 30 to 40 C. in a neutral to Weakly alkaline medium with theamine or with the amino-sulfonic acid.

The reaction of the gelatin with the heterocyclic halogen compoundgenerally proceeds easily Without recourse to special measures. Forexample, an aqueous solution of the heterocyclic compound may be broughtinto contact with the gelatin at a slightly raised temperature, forexample, about 40 C. In most cases nothing happens for a long time. Itis not until the gelatin has been dried and after a further interval oftime that the halogen compound reacts with the gelatin, and the quantityof hydrohalic acid liberated thereby With respect to the proportions ofthe two reactants that actually react is so small that it is smoothlybuffered by the excess of gelatin.

The degree of hardness of the gelatin brought about by the reactionvaries depending on the constitution and proportion of the halogencompound used. The proportion of the halogen compound used isadvantageously about 1 to 5%, calculated on the gelatin present. Ameasure of the degree of hardness produced can be obtained bydetermining the temperature at which the gelatin layer melts off thesupport when the layer is in contact with water of which the temperatureis gradually increased.

It is noteworthy, and by no means predictable, that the reaction of theheterocyclic halogen compound with the gelatin produces a hardeningeffect when the heteocyclic compound contains only one reactive halogenatom. If a plurality of reactive halogen atoms is present in themolecule of the heterocyclic halogen compound, as in the HO S case, forexample, with the compounds of the Formulae (a) to (e), the gelatin ishardened to a high degree, apparently owing to extensive cross-linking.In this case the groups imparting solubility in water in theheterocyclic halogen compound in no way impair the hardening elfect.They have the effect of maintaining a good swelling capacity, in spiteof the hardening, which is desirable. The hardening of gelatin by themethod of the invention does not impair the sensitivity of the silverhalide, nor does it impair the reactivity of color couplers ordyestuffs.

The following examples illustrate the invention, the parts andpercentages being by Weight.

Example 1 An aqueous solution A was prepared which contained 5% of thehardener of Formula (b) (2:4-dichloro-6-phenylamino-l:3:5-triazine-3'-sulfonic acid). Of this solution Aditferent quantities, viz. 2 parts, 4 parts and 6 parts, were admixedeach with 120 parts of an aqueous silver bromide-silver chlorideemulsion containing 10 parts of gelatin in the 120 parts of emulsion.The so-obtained mixtures contained 1% or 2% or 3% of the compound ofFormula (b), calculated on dry gelatin. The mixtures were cast on glassplates. After being dried and subsequently stored for 24 to 48 hours,the emulsion layers had the following melting points:

Percentage of hardening agent calculated on the gelatine Melting pointsof the layers, C

Similar results were obtained by using in the same manner compounds ofthe Formulae (a), (c), (e) and (g) as hardening agents for the gelatin,instead of the compound of the Formula (b). These compounds can beprepared by known methods. By exchanging one chlorine atom of thedichlorotriazine compounds for another substituent, for example, byusing the compound of the Formula (f), and the full degree of hardeningis not reached until after a longer period of storage.

The compound of the Formula (a) may be prepared as follows:

80 parts of cyanuric chloride are dissolved in 160 parts of acetone, andthe solution is poured on to a mixture of 400 parts of water and 400parts of ice. To the mixture is added a neutral solution of the sodiumsalt of 70 parts of 1-arninobenzene-4-sulfonic acid in 800 parts ofwater. The temperature is kept at 2 to 3 C. with ice. The mixture isstirred for 35 to 60 minutes until aminobenzene sulfonic acid can nolonger be detected. The acid liberated during the condensation isneutralized by the dropwise addition of about 240 parts of a sodiumcarbonate solution of 10% strength, so that the pH-value is maintainedat 7:05. When the condensation has finished,

8 the compound of the Formula (a) may be completely dissolved, and it issalted out by the addition of 150 parts of a saturated sodium chloridesolution. It is filtered off and dried in vacuo.

Example 2 To 100 parts of a silver bromide gelatin of 10% strength therewas added at 40 C. 0.2 part of the disazodyestutf of the formula OCH;;HO NHa dissolved in 20 parts of water and also 6 parts of a saponinesolution of 3% strength and 2 parts of 2:4-dichloro-6-phenylamino-l:325-triazine 2'14 disulfonic acid of theFormula (0) dissolved in 30 parts of water.

After casting the emulsion on safety film, and drying the layer andstoring it for 24 to 48 hours, there was obtained a silver. halide layerdyed blue, which, after exposure, could be converted by the silverdyestufi bleaching process into a blue component color image, and whichhaving a melting point of about C., withstands well the treatment bathswhich attack gelatin.

Example 3 To separate portions of a red-sensitized silver halideemulsion which, for every thousand parts by volume, contained 30 partsof silver chloride, 70 parts of gelatin and 15 parts of one of the colorcouplers suitable for color development and corresponding to the formulaOH X G -Q HN-O (ll-(CH2) w-O H Baths were prepared which contained -2 to10 parts of one of the chlorotriazine compounds of the Formulae (a),(b), (c), (e) and (g) dissolved in parts of'water.

These baths were used in the same way as conventional hardening baths,that is to say, the material to be hardened was treated in the bath for5 to 20 minutes, after which it was rinsed for 2 to 5 minutes, and thendried. After standing for 24 hours, the materials so treated were wellhardened.

The compound of the Formulae (i), (l), (m) and (n) were slower in theiraction. When used in proportions ranging from 2 to 6%, based on theweight of the gelatin, these compounds gave melting points from 40 C. to

65 C., depending on the proportion used, and they resulted in a greatertendency to swell which is desirable, for example, in imbibitionprocesses.

Example 5 4 parts of the compound of the Formula were dissolved in thecold in 100 parts of water. 10 parts of the solution so prepared wereadded to 100 parts of an aqueous solution of gelatine of 8 to 10%strength or to a corresponding silver halide emulsion at a temperatureof 35 to 38 C.

10 cc. of the mixture so prepared were cast on a glass plate measuring13 cm. x 18 cm., and the layer was allowed to solidify and dry. Themelting point of a. control layer not containing the hardening agent was32 C. The layer containing the hardening agent had a melting point of 42C., after 24 hours, which rose to 58 to 62 C. in the course of a fewdays.

The compound of the Formula (0) can be prepared by condensing in water80 parts of cyanuric chloride with 121 parts of2-amino-naphthalene-4:8-disulfouic acid in the team of its sodium salt,in the manner described at the end of Example 1.

Example 6 Gelatin emulsions were treated with 2 to based on the drygelatin content, of the compound of Formula (p), in the manner describedin Example 1. This compound can be prepared in the following manner: 110parts of the compound of Formula (a) are treated at 40 C. in 6000 partsof water with 24 parts of monoethanolamine and 20 parts of sodiumcarbonate. After 30 to 60 minutes, the condensation product isprecipitated with sodium chloride and dried.

By the above treatment melting point of the layer was raised to about 40C. This degree of hardening was obtained only after a certain period ofstorage. The reaction with the compound (p) has an especially favorableeffect on hot drying carried out on a machine.

Slow hardening also occurs when the gelatin is reacted in the mannerdescribed with the condensation product of the Formula (q). Thiscompound is obtained in a manner analogous to that described forobtaining the compound of the Formula (p), with the use of 12 parts ofethylene diamine, instead of the ethanolamine.

Example 7 Gelatin emulsions were treated with the compound of theFormula (r) in the manner described in Example 1. 24 hours aftercasting, the melting points of the emulsion layers were 68 C. to 62 C.and shortly rose to 90 C. and above. The compound of the Formula (r) isobtainable by reacting the sodium salt of 94 parts of lhydroxy-4aminobenzene-Z-carboxylic acid-6 sulfonic acid with 80 parts of cyanuricchloride.

Example 8 A gelatin emulsion was treated with the dichloropyrimidinecompound of the Formula (s) in the manner described in Example 1. Someconsiderable time elapsed before the gelatin reached its maximum degreeof hardness. The compound of the Formula (s) is obtainable in a manneranalogous to that described in Example 1 by condensing the sodium saltof 70 parts of l-aminobenzene-4-sulfonic acid with 73 parts of2:4:6-trichloropyrimidine which-has been dissolved in ethanol.

A similar etfect on the gelatin obtained with the trichloropyrimidinecompound of the Formula (t). This compound is prepared from224:5:6-tetrachloropyrimidine and the sodium salt of1-aminobenzene-4-sulfonic acid.

The pyrimidine compounds of the Formulae (s) and (t), which areconsiderably slower in their action than the triazine compounds, do notincrease the viscosity of the casting mixture during the time requiredfor casting large batches of the mixture. The freshly cast and driedlayers have melting points of about 40 C. The melting points rise aftera long period of storage.

Even slower in its action is the pyridazine compound of the Formula-(u), which may be prepared from tetrachloropyridazine and1-aminobenzene-3-sul-fonic acid.

What is claimed is:

1. A process for hardening gelatin which comprises reacting the gelatinwith a colorless compound which contains at least one acid groupimparting solubility in water, which group is bound to a carbon atom, atleast one heterocyclic six-membered ring, consisting of 3 to 4 carbonatoms and 2 to 3 nitrogen atoms and having three conjugated doublebonds, and at least one halogen atom bound to one of the ring carbonatoms of the heterocyclic ring, the carbon atoms in said heterocyclicring having substituents selected from the group consisting of theaforesaid acid group, a halogen atom, a sulfophenylarnino radical, asulfonaphthylamino radical, a sulfatoalkylamino radical, a sulfop-henoxyradical, a hydroxyalkylamino radical, a primary amino group, afi-(6-chloro-4- sulfophenylamino-1,3,5-triazine-2 ylamino)-ethylaminoradical, a 8-(6-chloro-4-sulfophenylamino-1,3,5-triazine-2-ylamino)-phenylamino radical, and a B-(6-chloro-4- sulfophenoxy 1,3,5triazine 2 ylamino)-et-hylamino radical.

2. Gelatin which has been hardened by reaction with a colorless compoundwhich contains at least one acid group imparting solubility in water,which group is bound to a carbon atom, at least one heterocyclicsix-membered ring consisting of 3 to 4 carbon atoms and 2 to 3 nitrogenatoms and having three conjugated double bonds, and at least one halogenatom bound to one of the ring carbon atoms of the heterocyclic ring, thecarbon atoms in said heterocyclic ring having substituents selected fromthe group consisting of the aforesaid acid group, a halogen atom, asulfophenylamino radical, a sulfonaphthylamino radical, asulfatoalkylamino radical, a sulfophenoxy radical, a hydroxyalk-ylaminoradical, a primary amino group, a B-(6 chloro-4 sulfophenylaimino- 1,3,5triazine-2- ylamino)-ethylamino radical, a[3-(6-chloro-4-sulfophenylamino-1,3,5-triazine-2-ylamino)-phenylaminoradical, and a ,8-(6-chloro-4-sulfophenoxy-1,3,5 triazine-2-ylamino)-ethylamino radical.

3. A process for hardening gelatin which comprises reacting the gelatinwith a colorless compound of the formula Halogen O-N N C-Halogon inwhich R represents a benzene radical containing at least one sulfonicacid group.

5. A process for hardening gelatin which comprises reacting the gelatinwith a colorless compound of the formula HNR1 in which R represents anaromatic radical of the composition 0 ,11 (SO H) where m and n eachrepresents a whole number of at the most 2.

6. A process for hardening gelatin which comprises reacting the gelatinwith the compound of the formula References Cited by the Examiner UNITEDSTATES PATENTS I Kaszuba 961 11 OTHER REFERENCES Wegmann: Textii-Praxis(October 1958), pages 1056- 61.

Advances in Protein Chemistry, volume II, page 111.

Noller: Chemistry of Organic Compounds, pp. 466.

WILLIAM H. SHORT, Primary Examiner.

LEON ZITVER, Examiner.

20 D. P. CLARKE, H. SCHAIN, Assistant Examiner UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent No 3 288 ,775 November 29 1966Walter Anderau et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below In the heading to the printed specification, after line9, insert Claims priority, application Switzerland,

April 7, 1961, 4074/61 column 10, lines 49 to 56, the right-hand portionof the formula, for "Halogen" read Halogen Signed and sealed this 7thday of November 1967.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer

1. A PROCESS FOR HARDENING GELATIN WHICH COMPRISES REACTING THE GELATINWITH A COLORLESS COMPOUND WHICH CONTAINS AT LEAST ONE ACID GROUPIMPARTING SOLUBILITY IN WATER, WHICH GROUP IS BOUND TO A CARBON ATOM, ATLEAST ONE HETEROCYCLIC SIX-MEMBERED RING CONSISTING OF 3 TO 4 CARBONATOMS AND 2 TO 3 NITROGEN ATOMS AND HAVING THREE CONJUGATED DOUBLEBONDS, AND AT LEAST ONE HALOGEN ATOM BOUND TO ONE OF THE RING CARBONATOMS OF THE HETEROCYCLIC RING, THE CARBON ATOMS IN SAID HETEROCYCLICRING HAVING SUBSTITUENTS SELECTED FROM THE GROUP CONSISTING OF THEAFORESAID ACID GROUP, A HALOGEN ATOM, A SULFOPHENYLAMINO RADICAL, ASULFONAPHTHYLAMINO RADICAL, A SULFATOALKYLAMINO RADICAL, A SULFOPHENOXYRADICAL, A HYDROXYALKYLAMINO RADICAL, A PRIMARY AMINO GROUP, AB-(6-CHLORO-4: SULFOPHENYLAMINO-1,3,5-TRIAZINE-2- YLAMINO)-ETHYLAMINORADICAL, AB-(6-CHLORO-4-SULFOPHENYLAMINO-1,3,5-TRIAZINE2-YLAMINO)-PHENYLAMINORADICAL, AND A B-(6-CHLORO-4SULFOPHENOXY -1,3,5 - TRIAZINE- 2-YLAMINO)-ETHYLAMINO RADICAL.